Please explaine me this circuit!

[bt87]

can any body explain me what is:
"timer frequency set" in this circuit?

 

[bongkk]

Actually should read "frequency setting trimmer ". It is a variable capacitor and is used to fine tune the transmit frequency to match the cell phone freq.

 

[Awarapunshee]

can any body explain me what is:
"timer frequency set" in this circuit?

If I am not mistaken, then the output frequency (from the 555 pin3) calculation comes out to be 8.4MHz with the present set of resistors (6.8K+82K) and capacitor (1pF). I don't think that a 555 even with CMOS version can handle such a high frequency>>>

 

[FvM]

I don't think that a 555 even with CMOS version can handle such a high frequency

Yes, but what's the conclusion? Obviously, your formula doesn't apply. Did anybody claim, it should? I assume, it's still operating, but at a lower frequency, may be 1 MHz. Considering the obscure precision values of some parts, some values may be simply mistyped.

Generally, it looks like a kind of rather uneffective cell phone jammer, a transmitter not taking care of any serious RF regulations anyway. A toy for bored school boys.

 

[E-design]

I agree that it looks like some crude cell phone jammer. The 555 may be used as an attempt to FM modulate the osc to cover the cell band.

 

[bt87]

vll tht is a jammer cct but did't implemented that one!!!!

 

[deepuj]

This schematic seems like a failed attempt to design a jammer... The Hartley oscillator is wired for approximately 513MHz and the 555 timer output (obviously a wrong design... the chip cannot handle more than 1MHz... and it is not true that it will create a 1MHz even if it is designed for a much higher frequency.. 8.4MHz)...

I think he basic aim was to mix the two frequencies... (f1+f2 or f1+2f2 ...) Still it is really hard to reach the cell band... The harmonics will not be that strong!